I always say to add 1500lbs to a trailers dry weight. this will get you close to its loaded ready to travel weight. that would put a 5800lb trailer at a loaded weight of 7300lbs with 12.5% tongue weight of approx. 960lbs (you will need to load the trailer properly to arrive at this number).
As far as towing at 55-60, that will not be practical. you will get run off the highway at those speeds. I`ve run at 70 on occasion and it still isn't fast enough for most people. the 6.0 can handle it. I would think you will be OK. if your willing to get a new Tow Vehicle then why not tow with it to see how it does. then you can decide if you want something different. and with as many people that will be in the trailer you do not want to go smaller!
